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The plant cell.
The flow of energy
vacuoles
Vacuoles have a single membrane: The tonoplast
Expansion of plant cells occurs mainly in the vacuole so that this is the largest
compartment of most mature cells.
Main functions of the vacuole
• Isolating materials that might be harmful or a
threat to the cell
• Containing waste products
• Maintaining internal hydrostatic pressure or
turgor within the cell
• Maintaining an acidic internal pH
• Containing small molecules (anthocyanins for
color)
• Exporting unwanted substances from the cell
• Allows plants to support structures such as
leaves and flowers due to the pressure of the
central vacuole
Plamolysis
Others components of the cell wall
The cell wall is a cross-linked matrix
of:
Cellulose
Lignine
Hemicelluloses: regulate the cell
enlargement
Pectins: attract water to the walls
and form the middle lamella
Glycoproteins: structural proteins
The arrow indicates the middle lamella
(ML) holding the cell walls together.
Primary cell walls
Cellular undifferentiation
Support Primary cell walls
Unevenly thickened walls.
Primary pit fields and plasmodesmate Secondary wall
Alkaloids
Collenchyma
elongated cells with unevenly
thickened walls.
Simple pits and pit-pairs structural support for shoots and
leaves
cellulose and pectin.
Sclerenchyma
Tissues that have ceased
elongation.
Mature sclerenchyma is
composed of dead cells
Cellulose, hemicellulose,
and lignin.
Fibres and sclereids
Secondary wall
Sclereids are small bundles of sclerenchyma tissue in plants that form durable
layers, such as the cores of apples and the gritty texture of pears.
astrosclereids Cell wall
In a secondary wall commonly we can find
S1 Outer layer
S2 Middle layer
S3 Inner layer
In order to increase the thickness and the surface area new cellulose
microfibrils are placed on top of those previously formed
Cellulose synthase
expansines
Flow of energy
The laws of thermodynamics
1st “energy change”
2nd potential energy at the final state < potential energy of the
initial state
Exergonic reactions
Endergonic reactions
Solar radiation and photosynthesis are the better examples of
thermodynamic laws and exergonic reactions.
Flow of energy
Difussion, osmosis, turger
Redox reactions
Photosynthesis Cellular respira1on Energy of activation
An enzyme speeds up a chemical reac4on by lowering its energy of ac4va4on, the energy that must be supplied in order for molecules to react with one another. Temperature and ph and enzymes
Temperature and ph and enzymes
Define tonoplast What is plasmolysis? Why are pec4nes important? What is the difference between primary pit fields and plasmodesmata?
What are sclereids?
Draw the structure of the complete cell wall
What is the difference between endergonic and exergonic reactions?
Define energy of ac4va4on